docs: def trustRootValid(self):
          """Is my return_to under my trust_root?
  
          @returntype: bool
          """
          if not self.trust_root:
              return True
          tr = TrustRoot.parse(self.trust_root)
          if tr is None:
              raise MalformedTrustRoot(self.message, self.trust_root)
  
          if self.return_to is not None:
              return tr.validateURL(self.return_to)
          else:
              return True